1. Field of the Invention
The present invention relates to an electric connection box mounted to a vehicle such as a passenger car.
2. Discussion of Background
To satisfy a growing demand for improved passenger comfort, the electrical components mounted in a vehicle are increasing in number, which components may include audio system, navigation system, television, electrically-powered antenna, air conditioner, rear-wind heater, seat heater, electrically-powered seat, and suspension-stiffness controller.
The vehicle-mounted electrical components are supplied with electric power from a battery and operated under the control of a controller. Usually, the battery and the controller are disposed in the engine room and the passenger compartment, respectively, whereas the vehicle-mounted electrical components are disposed at various parts of the vehicle body, so that complicated wiring is required for electrical connection between the vehicle-mounted electrical components, the battery and the controller. For convenience of wiring, an electric connection box and wire harnesses are generally employed, the harnesses extending between the connection box, the battery, and the controller.
An electrical connection box is exemplarily shown at 50 in FIG. 5. The connection box 50 mainly includes: upper and lower cases 51, 52 assembled into one piece; a wiring board 53 interposed between the upper and lower cases 51, 52; and bus bars 55, 56 mounted on opposite first and second surfaces, respectively, of the wiring board 53 for distributing large electric currents. Electrical parts, including fuses, relays, and terminals, adapted for connection with wire harnesses, are mounted on the upper and lower cases 51, 52. The fuses serve as protective measures against overcurrent that can be generated when a wire harness is short-circuited with the vehicle body or an electric load, such as an electric motor, becomes faulty for any reason.
The wiring board 53, formed by resin injection molding, for instance, is formed with reinforcing ribs for providing the wiring board 53 with desired mechanical strength and vibration resistance. The wiring board 53 has opposite faces thereof formed with wiring grooves in which continuous wires W are installed with the use of a wiring machine. The continuous wire W are cut, where required, to form desired electrical connecting circuits. Further, press-fitted terminals 54 for establishing electrical connection between corresponding ones one the wires and the electrical parts, such as fuses, are mounted on the wiring board 53. The wiring board 53 cooperates with the wires W, the terminals 54, and the bus bars 55, 56, to constitute an electrical connecting component (internal component) 57 received in the upper and lower cases 51, 52.
To fabricate electrical connecting components 57 each having a number of constituent elements, such as the wire W, the wiring board 53, the terminals 54, and the bus bars 55, 56, complicated assembling work, which may include many steps, is required. Thus the cycle time for fabricating the electrical connecting component 57 is generally longer than that of a subsequent step of assembling the cases 51, 52 and the internal component 57 into one piece. This causes a reduction in production efficiency of electric connection boses. In order to improve the production efficiency by shortening an apparent cycle time of production of the electrical connecting component 57 to the extent that it becomes nearly equal to that of the subsequent assembling step, a plurality of production facilities, each including a wiring machine and a terminal press-fitting machine, can be employed for production of electrical connecting components 57 of the same kind.
Defective electrical connecting components 57 can be manufactured if any one of the production facilities is faulty in operation. For instance, if one of the wiring machines becomes faulty, wires W are inappropriately installed on the wiring boards 53 concerned. If a molding die for forming wiring boards 53 is defective or if an amount of resin injected is insufficient, a defective formation of reinforcing ribs can occur in the associated wiring boards 53. In such cases, defective products to be discarded must be discriminated from non-defective products. However, a proper discrimination of defective products cannot be made when a plurality of production facilities are employed for the production of electrical connecting components 57 in particular.
That is, if a faulty operation of a certain production facility has been overlooked for a long time and defective electrical connecting components have been one incorporated into the cases (casing) of electrical connecting boxes, it becomes impossible to specify those electrical connecting boxes, which accommodate defective components therein, by external inspection. Although electric connection boxes are labeled with an indication, such as a manufacturer's serial number, discrimination between defective products and non-defective products cannot usually be made based on the serial numbers alone. Thus, all the products, including defective and non-defective products manufactured during the period in which at least one production facility was abnormally operated, must be repaired or discarded to eliminate the fear of shipment of defective products, resulting in a waste in costs.